In prior years it would not be uncommon for an individual to obtain content (e.g., literary works, periodicals, music, and movies) from a retail location in the form of a physical medium. For example, an individual might travel to a local bookstore and purchase written works in the form of a book, newspaper, or magazine. In another example, an individual might purchase music stored on a Compact Disc (CD) or a motion picture stored on a Digital Video Disc (DVD). In recent years the ubiquity of the Internet and the World Wide Web has paved the way for alternative methods of obtaining and consuming content. For example, a user might log on to a music retailer's website and download a digital version of a music album. In other example, a user might log on to a movie subscription provider's website to download or stream a motion picture to view on a personal computer. In the case of books, a user might log on to a bookseller's website and download an electronic book (“e-book”) for view on a computer system, such as a desktop computer or a handheld e-book reader.
The Internet and World Wide Web serve as a backbone for numerous file sharing mechanisms. Examples of such mechanisms include electronic mail (“email”) and more advanced file distribution software, such as peer-to-peer (“P2P”) file sharing applications. In many cases, such file sharing mechanisms are often utilized to distribute electronic content to individuals that are not authorized to access such content. Such distribution is likely due in part to the relative ease and anonymity of sharing files through such mechanisms. To combat unauthorized consumption of content, some content owners have adopted an approach to protecting their content known as digital rights management (“DRM”), which may include various techniques for limiting access of electronic content to authorized individuals and/or enforcing other restrictions on the use of such content.
Content providers and advertisers often wish to measure the size, composition, and characteristics of the audience for programming content. For example, an advertiser in a television program may wish to know how many adults in a particular age group viewed a particular episode of a television program.
Traditionally, audience measurement data was collected through the use of surveys, diaries, or other manual reporting approaches. For example, in early implementations of the well-known Nielsen ratings for television audience measurement, viewers self-reported their viewing choices in written diaries. More recently, devices such as set meters have been used to automate some aspects of tracking the viewing habits of audiences.
When content to be measured is delivered in an unencrypted form, such as in an analog signal sent over a coaxial cable, it is a relatively simple matter to tap into the signal to monitor what a viewer is consuming. As noted above, however, in network settings such as the Internet, content providers often implement measures such as DRM to limit access to the content to authorized users only. In cases in which the files carrying the content are encrypted, a measuring entity may not be able to determine what content is being consumed by a viewer. One solution to this problem is to distribute to the measurement entities the keys for decrypting the content files. Such distribution may, however, create opportunities for unauthorized use and distribution of the content (if, for example, a hacker were to gain access to keys maintained by a measurement entity.)
Another approach to enable a measurement of encrypted content is through the use of content identification markers attached to encrypted files. For example, an identification tag may be placed in a metadata header of an encrypted content file. Such identification markers may, however, be susceptible to alteration, misuse, or error. For example, a program identifier meta-tag for one program might be substituted (either intentionally or unintentionally) with the program identifier meta-tag of a second program, thereby overstating the playbacks for the second program.